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Azure Virtual Machines are a powerful Infrastructure-as-a-Service product that offers a quick path to the cloud and a flexible solution to a number of scenarios.

One nice thing about Azure VMs is that you can easily scale them up or down as needed. So, as your needs change, you can ensure you have sufficient resources without paying for computing power you’re not using.

There is one important thing, however, to be aware of when choosing a VM size. Scaling a VM to another size within the same sizing series is easy, but switching to a different series is more complex and can require longer downtime.

So, if you anticipate needing to scale your new VM at some point, it is probably best to try to pick the right sizing series before you create the VM so that scaling later is an easy process.

Deciding What Series Fits Your Needs

The A, B, D, F, and G series are all general computing series, but with different focuses. The A series is well suited for development and light workloads, but if you think the VM will ever become a production server, then the A series is probably not right. Choosing between D, F and G is a question of deciding what your most likely bottleneck will be. If you think you’re likely to max out the CPU before you max out memory, then the F series is probably the right choice.

The H, L, and N series are premium series that are more targeted at special use cases. Read on for some details on each series below.

Within each series, you may find that there is a v2 or v3 attached to the name. This indicates a newer generation within the series. Newer generations usually indicate newer hardware and more features. When considering the ability to scale, you may find you can only scale within the same generation of your chosen series, so the generation is another factor to consider when choosing a series.

Azure Virtual Machines by Series

A Series - Entry-level economical VMs

A series VMs are best suited for testing and development purposes. They are not intended for production workloads.

B Series – General purpose compute with bursting

The B series is still in preview, but it is a general purpose compute platform for workloads with low average CPU utilization but occasional bursts. Compared to resource-equivalent VMs from other series, the B series is a more cost-effective option for bursty workloads. As your CPU utilization remains low, you build up credits that can be used for bursts. If you have low average CPU utilization but need to be able to occasionally burst to high CPU utilization, this series is a good option. Because it is still in preview, pricing, availability, and options are likely to change.

D Series – General purpose compute

D series VMs offer a balanced configuration for general workloads. When in doubt, choose a D series VM.

F Series – Compute optimized virtual machines

F series VMs are targeted for workloads that are CPU intensive. As you scale up, the number of vCPUs will grow faster relative to other resources compared to other VM series. Choose an F series VM if you know the CPU will be your main bottleneck.

G Series – Memory and storage optimized virtual machines

G series is the counterpart to F series. When you scale a G series VM, storage and memory will grow faster than the number of vCPUs compared to other VM series. Choose a G series VM if you anticipate high memory utilization.

H Series – High-performance virtual machines

The H series offers special high-performance hardware. Choose an H series VM if you are doing high-performance computing, such as simulations, fluid dynamics or analytics.

L Series – Storage optimized virtual machines

The L series offers high throughput high capacity storage options. These VMs are well suited to data-intensive applications, including data warehousing.

N Series – GPU enabled virtual machines

N series VMs include GPU (Graphics Processing Unit) capabilities. These high-end VMs are targeted at scenarios that require graphics or parallel processing capabilities.